All masquerade address tests fail with AssertionError: '127.0.0.1' != … with Python >= 3.9.3

[sbraz]

Hi, I'm pretty sure the cause of this is:

bpo-43285: ftplib no longer trusts the IP address value returned from the server in response to the PASV command by default. This prevents a malicious FTP server from using the response to probe IPv4 address and port combinations on the client network. Code that requires the former vulnerable behavior may set a trust_server_pasv_ipv4_address attribute on their ftplib.FTP instances to True to re-enable it.

This fix was applied to:

• 3.6.14
• 3.7.11
• 3.8.9
• 3.9.3

It causes the following failures with Python 3.9.3 (no problem with 3.9.2):

FAILED pyftpdlib/test/test_functional.py::TestConfigurableOptions::test_masquerade_address - AssertionError: '127.0.0.1' != '256.256.256.256'
FAILED pyftpdlib/test/test_functional.py::TestConfigurableOptions::test_masquerade_address_map - AssertionError: '127.0.0.1' != '128.128.128.128'
FAILED pyftpdlib/test/test_functional_ssl.py::TestConfigurableOptions::test_masquerade_address - AssertionError: '127.0.0.1' != '256.256.256.256'
FAILED pyftpdlib/test/test_functional_ssl.py::TestConfigurableOptions::test_masquerade_address_map - AssertionError: '127.0.0.1' != '128.128.128.128'
FAILED pyftpdlib/test/test_functional_ssl.py::TestConfigurableOptionsTLSMixin::test_masquerade_address - AssertionError: '127.0.0.1' != '256.256.256.256'
FAILED pyftpdlib/test/test_functional_ssl.py::TestConfigurableOptionsTLSMixin::test_masquerade_address_map - AssertionError: '127.0.0.1' != '128.128.128.128'

Here's the exact error from the first one:

_________________________________________________________________________________ TestConfigurableOptions.test_masquerade_address _________________________________________________________________________________
                                                                                                                                                                                                                   
self = <pyftpdlib.test.test_functional.TestConfigurableOptions testMethod=test_masquerade_address>       
                                                                                                                                                                                                                   
    def test_masquerade_address(self):                                                                                                                                                                             
        # Test FTPHandler.masquerade_address attribute                                                                                                                                                             
        self.server = self.server_class()                                                                                                                                                                          
        self.server.handler.masquerade_address = "256.256.256.256"                                                                                                                                                 
        self.server.start()                                                                                                                                                                                        
        self.connect()                                                                                                                                                                                             
        host, port = self.client.makepasv()                                                                                                                                                                        
>       self.assertEqual(host, "256.256.256.256")                                                        
E       AssertionError: '127.0.0.1' != '256.256.256.256'
E       - 127.0.0.1                              
E       + 256.256.256.256                                                                                

[Apteryks]

Reproduced with Python 3.9.9 on GNU Guix.